This invention relates to improvements in high speed mail sorting equipment of the type disclosed in pending patent application Ser. No. 973,926, filed Dec. 28, 1978 in the name of Roy Akers now U.S. Pat. No. 4,275,875 issued June 30, 1981.
One of the major problems associated with high speed mail sorting machines is to assure that the envelopes are properly separated from one another for individual handling. If two or more envelopes stick together and are advanced together through the machine rather than individually, they are deposited incorrectly in the same sorting bin. The jogger arm mechanism shown in the aforementioned Akers application represents one approach to this problem that has proven to be successful for the most part. Nevertheless, the jogger arms rely on shaking the entire supply stack of envelopes rather than providing positive separation of the envelopes from one another, and the effectiveness of the separation suffers accordingly.
Another problem in this type of equipment is to maintain the envelopes in the magazine oriented properly to be picked off at the envelope feed station. As shown in the Akers application, the magazine is typically provided with a carriage which rides on conveyor belts to advance the envelope supply toward the feed station. Switches at the feed station sense the presence or absence of envelopes and control the conveyor motor accordingly. The carriage compresses the envelopes rather firmly, and the envelopes are thus subjected to possible wrinkling or other damage unless they are initially organized in a neatly arranged stack. Also, if the carriage of a significant quantity of envelopes become skewed in the magazine, the leading envelope can be skewed or otherwise improperly oriented such that it is not picked off properly by the suction belt arrangement at the envelope feed station.
It is the primary goal of the present invention to provide a mail sorting machine having an improved pick off device for separating the individual envelopes and an improved conveyor in the magazine section of the machine for delivering the envelopes to the pick off device in the proper orientation for effective separation.
In accordance with the invention, the magazine section of the machine is equipped with a screw conveyor having four parallel rollers with spiral grooves for receiving the lower edges of the envelopes which are loaded in the magazine. A pair of raised rollers with identical spiral grooves engage the ends of the envelopes to maintain them each in a vertical orientation as they travel along the conveyor. As the envelopes approach the feed station located at the end of the magazine, they contact switch arms which control the drive motors of the rollers in a manner to assure that the envelopes are not skewed. The envelopes are thus conveyed along the magazine in the proper orientation and are not crushed tightly against one another as occurs in other types of conveyors.
The pick off device includes a pair of belts and an associated vacuum box which draws the leading envelope against the belts. An extra envelope adhering to the leading envelope is exposed to a second vacuum box and drawn by it away from the belts until the leading envelope clears the first vacuum box, at which time the extra envelope is drawn against the belts by the stronger suction force of the first vacuum. The impact surface of the second vacuum box is beveled to provide "shingling" of the envelopes if more than one extra envelope sticks to the leading envelope. The overall result is that the individual envelopes are effectively separated from the stack and do not stick together as they are advanced through the machine and eventually deposited in the appropriate bins.